# Horse chestnut (Aesculus hippocastanum) **Aesculus hippocastanum* L.; *Hippocastanum vulgare* Gaertn.; in pharmacy *Hippocastani semen*, the seed, and *Hippocastani cortex*, the bark* **Known today as.** *Aesculus hippocastanum*, a tall, fast-growing tree of the family Sapindaceae, with an erect, columnar trunk, smooth grey-green bark, and large leaves of five or seven toothed leaflets spreading like the fingers of a hand. Its flowers, mostly white with a reddish tinge, grow in dense, erect spikes, and its fruit is a brown nut with “a very shining, polished skin” in a spiny green husk that splits in three. Grieve, who says it was introduced into England about the middle of the sixteenth century, insists it is “an entirely different tree from the Sweet Chestnut, to which it is not even distantly related.” Kind: Plant > **Caution.** If there is inflammation of the skin, thrombophlebitis, hardening under the skin, ulcers, sudden swelling of one or both legs, or heart or kidney failure, the European agency advises consulting a doctor; likewise for rectal bleeding in someone using it for haemorrhoids. It is not recommended under eighteen, nor in pregnancy and breast-feeding for lack of data. Stomach complaints, headache, vertigo, itching, and allergic reactions have been reported. LiverTox notes that the seeds contain the toxic saponin escin, which commercial preparations remove, and that horse chestnut “has been implicated in rare instances of clinically apparent liver injury,” mild and self-limited, with no instance of liver failure or death. ## What was it used for? Grieve gives the bark as tonic, narcotic, and febrifuge, used in an infusion for intermittent fevers and outwardly on ulcers, and the fruits as “employed in the treatment of rheumatism and neuralgia, and also in rectal complaints and for haemorrhoids.” Its modern use is for the veins of the legs. ## What does modern science say? The European Medicines Agency’s herbal committee accepts dry extracts of the seed on clinical evidence, as ‘well-established use,’ for chronic venous insufficiency, “characterised by swollen legs, varicose veins, a feeling of heaviness, pain, tiredness, itching, tension and cramps in the calves” (monograph of 2020). As traditional herbal medicines, “exclusively based upon long-standing use,” it accepts seed preparations for heavy, uncomfortable legs from minor venous circulatory disturbances and for the signs of bruises, and the bark for the same complaint of the legs and for the itching and burning of haemorrhoids once a doctor has excluded serious conditions (bark monograph of 2023). Its assessment reports find 3 to 10 per cent of triterpene saponins in the seed, with a high proportion of starch, and coumarin derivatives such as esculin and fraxin, up to 7 per cent, as the most characteristic compounds of the bark; the coumarins are absent from the seed. A Cochrane review of 2012 found that leg pain was significantly reduced against placebo in six of seven trials and leg volume reduced in six trials of 502 patients, with mild and infrequent adverse events, and judged the extract an efficacious and safe short-term treatment, though larger trials were needed to confirm it. ## Pharmacognosy and toxicology - **triterpene saponins**: 3 to 10 per cent of the seed - **escin**: the toxic saponin of the seed, removed from commercial preparations - **esculin**: a coumarin, with fraxin up to 7 per cent of the bark; absent from the seed - **fraxin**: **Mechanism.** Not established in the sources read for this entry. **Standing.** European Union herbal monographs: well-established use of seed extracts for chronic venous insufficiency (2020), and traditional use, “exclusively based upon long-standing use,” of the seed and the bark (2023). A Cochrane review (2012) judged the seed extract efficacious and safe in the short term. ## What lore surrounds it? On the small branches are scars where the leaves have fallen, each “a perfect facsimile of a horse-shoe, even to the seven nail markings,” from which, Grieve thought, the tree perhaps takes its name. The nuts were tried as fodder at Wye College, where a calf throve on the meal and a sheep took no harm, but the pig refused it; experiments in the Great War showed, Grieve reports, that every ton of horse chestnuts harvested saved half a ton of grain for people to eat. ## What did the older authorities say? **Grieve, *A Modern Herbal* (1931).** The name *Aesculus*, from *esca*, food, was first given to an oak which, according to Pliny, was highly prized for its acorns; how it passed to this tree is “very uncertain,” perhaps, as Loudon suggests, ironically, the nuts looking like sweet chestnuts but being unfit to eat. *Hippocastanum* translates the common name, which Evelyn says was given “from its curing horses brokenwinded and other cattle of coughs”; some writers, Grieve adds, think ‘horse’ a corruption of the Welsh *gwres*, hot or pungent, making it the bitter chestnut beside the sweet. ## Sources - Grieve, M. *A Modern Herbal*, “Chestnut, Horse.” As published on botanical.com. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Hippocastani semen (Horse-Chestnut Seed)*. EMA/HMPC/628242/2018, 15 January 2020. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Hippocastani cortex (Horse-chestnut bark)*. EMA/HMPC/596130/2022, 22 November 2023. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Hippocastani semen*. EMA/HMPC/638244/2018, 15 January 2020. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Hippocastani cortex*. EMA/HMPC/596131/2022, 22 November 2023. - Pittler MH & Ernst E (2012). Horse chestnut seed extract for chronic venous insufficiency. *The Cochrane database of systematic reviews*. PMID 23152216. - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “HorseChestnut.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2018. NCBI Bookshelf. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Hippocastani semen (Horse-Chestnut Seed)*. EMA/HMPC/628242/2018, 15 January 2020. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Hippocastani cortex (Horse-chestnut bark)*. EMA/HMPC/596130/2022, 22 November 2023. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Hippocastani semen*. EMA/HMPC/638244/2018, 15 January 2020. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Hippocastani cortex*. EMA/HMPC/596131/2022, 22 November 2023. - Pittler MH & Ernst E (2012). Horse chestnut seed extract for chronic venous insufficiency. *The Cochrane database of systematic reviews*. PMID 23152216. - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “HorseChestnut.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2018. NCBI Bookshelf. --- *Horse chestnut.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-16. The Thinking Press. https://thethinkingpress.org/materia-medica/horse-chestnut Historical description, not medical advice.